Fluid Mosaic Model Of Phospholipids

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1. Diagram an individual phospholipid and a bilayer of phospholipids. Label the hydrophilic head, and hydrophobic tails in both.

2. Explain the Fluid Mosaic model of the cell membrane and describe the functions of the proteins that are embedded in the membrane.
The Fluid Mosaic model of the cell membrane is a hypothesis that describes the phospholipid bilayer and it proteins. It states that the membrane is flexible - fluid - and has various proteins embedded in it - a mosaic. These structures are in constant motion. Proposed by Singer and NIcolson in 1972, they asserted that proteins are inserted in the membrane, with the hydrophobic regions interacting with the hydrophobic tails and the hydrophilic regions interacting with the hydrophobic
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Thus, it relates to energy transfer, as energy is transformed or transferred as entropy increases. When the concentration of a substance of two sides of a barrier have reached equilibrium, or equal concentration, there is no concentration gradient, or movement from high concentration to low concentration. When a concentration gradient exists, there is a state of entropy, and thus a state favorable to energy. As substances diffuse, they become less ordered: a state of entropy and a desired state for energy.
6. How is active transport possible, since it contradicts the tendencies of the second law of thermodynamics?
Active transport utilizes proteins and ATP to moves substance against its concentration gradient. The protein changes shape with the ATP to move a substance across the membrane, to where it is more concentrated. This process increases entropy in the highly concentrated side of the membrane and decreases entropy on the other side. Ergo, it contradicts the second law of thermodynamics by defying equilibrium. Yet, it can still be done with ATP and carrier proteins, which transport the substance in its compartment that changes shape to allow the substance in and out.
7. Diagram one complete cycle of the Sodium-Potassium pump. Is this active or passive
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8. Is it possible for a solution to be both hypertonic and hypotonic? Why or Why not?
It is possible for a solution to be both hypertonic and hypotonic due to the fact that these states of being are relative to a cell's, or any other membrane-bound structure’s, individual composition. FOr instance, is a cell has less of the solute than this environment, it would be hypertonic. If a cell had more of this solute, this environment would be hypotonic. Note, this is also true if the solution is hypertonic relative to cell, which then allows the solution to diffusion and pass actively into its membrane, causing it to be hypotonic.
9. How do large molecules get taken into or removed from the cell?
Large molecules are transported in and out of cells by exocytosis and endocytosis. The former relates to when a cell disposes of its large biological molecules by vesicles which fuse to the plasma membrane. This is mainly done by secretory cells and gets rid of substances like insulin or neurotransmitters. Endocytosis, however, allows the cell to take in substances. Vesicles pinch off from the plasma membrane, allowing the bulk into the cell. Endocytosis comes in three forms: phagocytosis, when a cell engulfs a substance entirely, pinocytosis, when the cell takes the substance in by small vesicles (like small gulps), and receptor-mediated endocytosis, where the substance binds to receptors,

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